Production of food products by reconstitution of comminuted materials by shaping the comminuted materials with the aid of gums and gel-forming materials, by mechanical methods such as extruding and molding, as well as by thermal treatment such as heating or cooling, are common practices in the food industry. Various processes are known for the production of such shaped food products. Many of these processes are based on the use of a gel forming system comprising an alginate and a bivalent cation such as the calcium ion.
One type of process employing these materials produces a shaped product encased in a skin, such as a sausage. For example, U.S. Pat. Nos. 3,650,765 and 3,650,766 disclose food products which are manufactured in any shape or size by a process including the steps of forming an extrudable slurry of a food material, extruding the slurry and forming a gel-like skin around the extruded product. The skin is formed by subjecting gelable materials such as alginates to the action of gelation agents such as alkaline earth ions, at the surface of the extrusion product. U.S. Pat. Nos. 3,891,776; 3,922,360; 4,117,172 and 3,676,158 also disclose similar processes whereby a shaped food product encased in a skin is formed. Some of these processes produce a peelable, self-supporting skin. When the skin is peeled off and the resulting product is again subjected to a bivalent cation solution, a skin is again formed.
Other processes based on the use of alginates and calcium ions produce a stabilized food product where the alginate contained in the slurry used for production is converted throughout into a complete advanced gel. For example, U.S. Pat. No. 2,791,508 discloses a process for producing reconstituted food products comprising initially forming a thixotropic semi-gel like substance by dispersing a comminuted, powdered, granulated or shredded foodstuff in a water solution of an edible hydrophilic colloid in which the dispersed foodstuff is present as discreet particles more or less completely enclosed in a matrix of the colloid gel. Alginates are disclosed as useful hydrophilic colloids. In addition, a gelation agent such as calcium carbonate must be added to the dispersed foodstuff and hydrophilic colloid to institute gelation. The time at which the gelation agent is added to the dispersion of foodstuff and hydrophilic colloid is critical since when the gelation agent is added, it liberates calcium ions which rapidly react with the colloid thereby forming a gel. Since this gelation occurs rapidly, it is necessary to quickly transfer the substance to an extruding feed pipe wherein the final advanced gel structure is formed. The feed pipe must be of such a length that the ensuing mixture becomes an advance gel substantially simultaneous with its exit. This is a major disadvantage since if the gelation agent is added too soon, the mixture will become an advanced gel before it exits the extruder thereby creating a blockage in the extruder mechanism. If, on the other hand, the gelation agent is added too late, the mixture will not become an advanced gel when it exits the extruder, thereby preventing the formation of a shaped food product.
Thus, the above prior art processes may result in both production and product difficulties, such as undesired skin formation, undesired finished product texture, and difficulties during extrusion.
Accordingly, it is among the objects of the present invention to provide an improved process for producing shaped food products which will insure both a smooth production run and a control of the desired characteristics of the finished product.